sql-server-samples/samples/features/sql-clr/TransitiveClosure

Implementing Transitive Closure Clustering in SQL Server using CLR UDF

SQL Database don't have built-in support for transitive closure clustering, so the only workaround is to implement this algorithm in .Net framework and expose it as T-SQL function. This code sample demonstrates how to create CLR User-Defined aggregate that implements clustering.

Contents

About this sample
Build the CLR/RegEx functions
Add RegEx functions to your SQL database
Test the functions
Disclaimers

About this sample

1. Applies to: SQL Server 2016+ Enterprise / Developer / Evaluation Edition
2. Key features:
   • CLR, JSON
3. Programming Language: .NET C#
4. Author: Davide Mauri, Jovan Popovic [jovanpop-msft]

Build the CLR/RegEx functions

1. Download the source code and open the solution using Visual Studio.
2. Change the password in .pfk file and rebuild the solution in Release mode.
3. Open and save TransitiveClosure.tt to generate output T-SQL file that will contain script that inserts .dll file with the Transitive closure clustering aggregate.

Add Clustering aggregate to your SQL database

File TransitiveClosure.sql contains the code that will import aggregate into SQL Database.

If you have not added CLR assemblies in your database, you should use the following script to enable CLR:

sp_configure @configname=clr_enabled, @configvalue=1
GO
RECONFIGURE
GO

Once you enable CLR, you can use the T-SQL script to add the clustering aggregate. The script depends on the location where you have built the project, and might look like:

CREATE ASSEMBLY TransitiveClosure FROM 'D:\GitHub\sql-server-samples\samples\features\sql-clr\TransitiveClosure\bin\Release\TransitiveClosureAggregatorLibrary.dll' WITH PERMISSION_SET = SAFE;
GO

CREATE SCHEMA TC;
GO

CREATE AGGREGATE TC.CLUSTERING(@id1 INT, @id2 INT)  
RETURNS NVARCHAR(MAX)  
EXTERNAL NAME TransitiveClosure.[TransitiveClosure.Aggregate]; 

This code will import assembly in SQL Database and add three functions that provide clustering functionalities.

Test the function

Once you create the assembly and expose the functions, you can use it to cluster some relational data in T-SQL code:

declare @edges table(n1 int, n2 int);

insert into @edges
values (1,2),(2,3),(3,4),(4,5),(2,21),(2,22),
              (7,8),(8,9),(9,10);

select TC.CLUSTERING(n1,n2)
from @edges;

Disclaimers

The code included in this sample is not intended to be a set of best practices on how to build scalable enterprise grade applications. This is beyond the scope of this sample.